Conventionally, cathode-ray tubes("CRT") or bulbs are used for display panel. However, the CRT's or bulbs consume large amount of electric power and generate a lot of heat when used for display panel. Especially, when a display panel uses bulbs as display elements, a colored glass is needed to represent a pixel and 7 Watts of electric power is consumed for each bulb. Further, since the lifetime of each bulb is 8,000 to 10,000 hours, the cost for maintenance and repair is very high.
As information society is coming, technologies for displaying high quality information on flat panel displays are rapidly developed. Further, since the high quality display system can be used in a variety of everyday life as well as special technical field including military and aviation, the needs for the high quality display system is rapidly growing. Therefore, it is required to develop a display device having characteristics of high efficiency, wide width, light weight, small unit pixel, broad visual angle, high resolution and natural colors.
The development of display technologies using semiconductor light emitting devices is delayed due to the difficulties in making blue color light emitting devices and green color light emitting devices. Recently, wide band gap compound semiconductors, such as SiC, AlN, GaN, ZnSe, are studied to be applied to short wavelength optical devices. In 1994, a blue color light emitting diode("LED") has been put to practical use. These compound semiconductors have advantages of high thermal stabilities, wide controllabilties of energy gaps, high radiation efficiencies and long life time even if there are some defects in the devices. Further, they can radiate lights of all frequency ranges of visible rays and a high molecule thin film structure has also been developed to be put to practical use.
As described above, the examples of natural color display a technologies are numerous in order to fulfill the needs for them. One of the examples is light emitting device for natural color display developed by Sharp Corporation("Sharp"). However, since the light emitting device of Sharp has a unit cell of which the size is 3 mm.times.3 mm, it is difficult to integrate those unit cells in a display panel.